Slide-out portions of vehicles have a flange at the inside end and a flange at the outside end with gaskets at each end that seal against either the inside surface of the stationary vehicle wall with the inside flange when the portion is extended, or against the outside surface of the stationary wall with the outside flange when the portion is retracted. The slide-out operating mechanism is usually at the bottom of the portion, so compressing the bottom gaskets is usually not a problem, but compressing the upper portions of the gaskets can be a problem, since the slide-out operating force is applied a relatively far distance from those portions. The present invention addresses this problem in an economical manner.